// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef GIN_MODULES_MODULE_REGISTRY_H_
#define GIN_MODULES_MODULE_REGISTRY_H_

#include <list>
#include <map>
#include <set>
#include <string>

#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "base/observer_list.h"
#include "gin/gin_export.h"
#include "v8/include/v8.h"

namespace gin {

class ModuleRegistryObserver;
struct PendingModule;

// This class implements the Asynchronous Module Definition (AMD) API.
// https://github.com/amdjs/amdjs-api/wiki/AMD
//
// Our implementation isn't complete yet. Missing features:
//   1) Built-in support for require, exports, and module.
//   2) Path resoltuion in module names.
//
// For these reasons, we don't have an "amd" property on the "define"
// function. The spec says we should only add that property once our
// implementation complies with the specification.
//
class GIN_EXPORT ModuleRegistry {
public:
    typedef base::Callback<void(v8::Local<v8::Value>)> LoadModuleCallback;

    virtual ~ModuleRegistry();

    static ModuleRegistry* From(v8::Local<v8::Context> context);

    static void RegisterGlobals(v8::Isolate* isolate,
        v8::Local<v8::ObjectTemplate> templ);

    // Installs the necessary functions needed for modules.
    // WARNING: this may execute script in the page.
    static bool InstallGlobals(v8::Isolate* isolate, v8::Local<v8::Object> obj);

    void AddObserver(ModuleRegistryObserver* observer);
    void RemoveObserver(ModuleRegistryObserver* observer);

    // The caller must have already entered our context.
    void AddBuiltinModule(v8::Isolate* isolate, const std::string& id,
        v8::Local<v8::Value> module);

    // The caller must have already entered our context.
    void AddPendingModule(v8::Isolate* isolate,
        scoped_ptr<PendingModule> pending);

    void LoadModule(v8::Isolate* isolate,
        const std::string& id,
        LoadModuleCallback callback);

    // The caller must have already entered our context.
    void AttemptToLoadMoreModules(v8::Isolate* isolate);

    const std::set<std::string>& available_modules() const
    {
        return available_modules_;
    }

    const std::set<std::string>& unsatisfied_dependencies() const
    {
        return unsatisfied_dependencies_;
    }

private:
    typedef ScopedVector<PendingModule> PendingModuleVector;
    typedef std::multimap<std::string, LoadModuleCallback> LoadModuleCallbackMap;

    explicit ModuleRegistry(v8::Isolate* isolate);

    bool Load(v8::Isolate* isolate, scoped_ptr<PendingModule> pending);
    bool RegisterModule(v8::Isolate* isolate,
        const std::string& id,
        v8::Local<v8::Value> module);

    bool CheckDependencies(PendingModule* pending);
    bool AttemptToLoad(v8::Isolate* isolate, scoped_ptr<PendingModule> pending);

    v8::Local<v8::Value> GetModule(v8::Isolate* isolate, const std::string& id);

    std::set<std::string> available_modules_;
    std::set<std::string> unsatisfied_dependencies_;

    LoadModuleCallbackMap waiting_callbacks_;

    PendingModuleVector pending_modules_;
    v8::Persistent<v8::Object> modules_;

    base::ObserverList<ModuleRegistryObserver> observer_list_;

    DISALLOW_COPY_AND_ASSIGN(ModuleRegistry);
};

} // namespace gin

#endif // GIN_MODULES_MODULE_REGISTRY_H_
